BRUSSELS (Reuters) - David Cameron set out
a last-ditch case against the nomination of Jean-Claude Juncker for
European Commission president on Friday, trying to enforce a point of
principle that raises the risk of Britain leaving the European Union.

The British prime minister sees the former Luxembourg premier as
lacking the will and the skills to reform the EU and told fellow
leaders bluntly they were about to make a mistake in backing him -
warning of unspecified 'consequences'.

But he was set to be outvoted 26-2 if, as expected, he insists on an
unprecedented vote among EU leaders.

Calling Juncker the wrong man for the job, Cameron said as he
arrived: "There are times when it's very important that you stick to
your principles and you stick to your convictions even if the odds
are heavily stacked against you rather than going along with
something that you believe is profoundly wrong.

"And today is one of those days."

The dispute is one of the most public and personal the European
Union has experienced in a decade, damaging efforts to present a
united front at a time when the bloc is recovering from an economic
crisis and keen to bolster its global image.

Despite Cameron's forthright opposition to Juncker, whose
centre-right political group won European Parliament elections last
month, Britain has failed to convince almost any of the 27 other
member states to support its position.

His sole remaining ally, Hungarian Prime Minister Viktor Orban,
reaffirmed on Friday that he would oppose Juncker if there was a
vote.

The nomination will be discussed over lunch on the second day of an
EU summit, which began on Thursday with a show of modern European
unity in a ceremony in the Belgian town of Ypres to commemorate the
centenary of World War One.

As well as the Commission presidency, one of the EU's most powerful
jobs with sway over legislation affecting 500 million people, the
summit will discuss energy policy after they signed free trade and
political association agreements with Ukraine, Georgia and Moldova,
increasing EU influence in the ex-Soviet east despite bitter
opposition from Moscow.

Leading EU officials insisted on Friday that the deals were not
targeted against Russia, with whom the bloc wants better relations.
But Ukrainian President Petro Poroshenko, voicing the unease with
which Moscow is viewed by many former satellites, urged the European
Union to help defend his borders and give it the prospect of full
membership - something the EU has resisted.

Elected last month, Poroshenko noted wryly he was signing the pact
with a pen stamped with the date of an EU meeting last November in
Vilnius. It was his Kremlin-backed predecessor's 11th-hour refusal
to sign the accord in Lithuania that sparked street protests which
forced him to flee to Russia in February.

"Historic events are unavoidable," Poroshenko said with a grin and a
flourish of the fateful pen.

CAMERON FORCES VOTE

While decisions among EU leaders are normally taken by consensus,
Cameron has said he will force a vote on Juncker - an unprecedented
move officials wanted to avoid but which now looks inevitable.

British officials acknowledge that he will lose, but say the prime
minister is determined to take a stand on principle, opposing not
only Juncker as a candidate but the process that led to his
selection in which the European Parliament effectively imposed its
preference on EU leaders.

Referring to last month's election to the EU legislature, in which
Cameron's Conservatives were beaten by a party that wants out of the
bloc, he said: "The European elections showed that there's huge
disquiet with the way the European Union works and yet the response
I believe is going to be wrong on two grounds.

"One on the grounds of principle - it is not right for the elected
heads of government of the European countries to give up their right
to nominate he head of the European Commission, the important role
in Europe. That is a bad principle. And it's the wrong person.
Jean-Claude Juncker has been at the heart of the project and
increased the power of Brussels and reduced the power of nation
states his entire working life."

Opinion polls show that many British voters support Cameron taking a
hard line on Europe. With the prime minister battling to shore up
support for his Conservative party and facing an election next year,
that popular support is critical.

But it leaves Cameron in an uncomfortable position towards his
fellow leaders, many of whom are now openly concerned about the
possibility of Britain moving inexorably towards the exit.

Cameron, many of whose own Conservatives favour a British exit from
the EU, or "Brexit", has promised voters a referendum on leaving the
bloc by 2017 - if he wins re-election next year.

A key threat to his re-election is the rise of the UK Independence
Party, which campaigns for leaving the EU and which topped last
month's European Parliament election in Britain.

Britain's northern European friends sought to play down the looming
clash on Friday and stressed they would work to keep Britain in the
union.

Swedish Prime Minister Fredrik Reinfeldt, who initially backed
Cameron, said he thought they had established the principle that the
so-called "Spitzenkandidaten" system would not pre-empt national
leaders' right to choose the Commission president in future. He said
he would back Juncker.

"We need the UK in the European Union," Danish Prime Minister Helle
Thorning-Schmidt, who is married to a Briton, told reporters, saying
she hoped the confrontation over Juncker would not do lasting
damage.

New Finnish Prime Minister Alexander Stubb, who has a British wife,
said: "I do not think that the UK is any closer to leaving and I
think it's very important that they stay in the European Union."

The problem is that if Juncker, a veteran Brussels dealmaker who is
committed to a more federal Europe, ends up heading the Commission,
it will be harder for Britain to renegotiate its relationship with
the EU, something Cameron has promised to do in advance of putting
membership to a referendum.

British officials concede that Juncker may make it harder to get a
renegotiation of membership terms and his presence may also increase
the likelihood that Britons vote to leave the EU.

British media have vilified Juncker personally, with one newspaper
saying his family had Nazi ties because his father was forced to
serve in the German army after it occupied Luxembourg, while another
focused on his drinking.

His successor as chairman of euro zone finance ministers, Jeroen
Dijsselbloem of the Netherlands, has said Juncker smoked and drank
heavily in meetings. Juncker has denied any alcohol problem.